Control of Highly Heat-Integrated Energy-Efficient Extractive Distillation Processes

In our previous papers, two highly heat integrated energy-efficient extractive distillation processes were presented by combining a preconcentration distillation column with an extractive distillation column or entrainer recovery column (Ind. Eng. Chem. Res. 2014, 53, 7121; Chem. Eng. Sri. 2015, 135, 166). However, these novel synthesis systems with highly heat-integrated configurations may exhibit complicated issues of dynamic controllability. Thus, this paper extends the previous work to investigate the dynamic controllabilities of these new synthesis systems. The singular value decomposition method is applied to analyze the temperature profiles and select the appropriate control trays. As the main column is highly heat-integrated from two columns, several degrees of freedom are lost. Thus, three temperature control loops are installed in the combined column. The dynamic performances of each system are tested by introducing +/- 20% disturbances of feed flow rate and composition, respectively. The results show that robust control can be achieved for both systems. The controllabilities of conventional three-column processes also have been explored and compared with that of synthesis systems.